Conversion of fuel nitrogen through HCN and NH3 to nitrogen oxides at elevated pressure

Abstract Reactions of fuel nitrogen during pyrolysis and combustion of pulverized HVb coal, two peats and fir back were studied experimentally in a pressurized entrained flow reactor at T = 1123 and 1273 K , p = 0.2, 0.4 and 0.8 MPa. Mass loss of fuel, release of C, N, H and O, and formation of NH 3 and HCN were measured during pyrolysis (in N 2 containing O 2 2 O and NO 2 through HCN and NH 3 were measured during combustion at 4–5 vol.% O 2 . The rate of pyrolysis of high-volatile fuels (fir bark and peat) increased with pressure. The reverse trend was found with HVb coal. The order of release of the elements studied from the fuel (O > H > C > N) was found to be independent of pressure. The HCN NH 3 ratio in the flame was dependent on the fuel-O fuel-N ratio and independent of pressure. Pressure did however increase the N 2 O NO ratio, because the concentrations of the key radicals in NO formation are decreased by pressure. With peats, the formation of N 2 O increased slightly with pressure. The emission of N 2 O however doubled with wood bark when the pressure increased from 0.2 to 0.8 MPa. Formation of NO 2 increased distinctly with pressure, and was fuel-dependent. One peat sample produced three times as much NO 2 as the other under identical conditions.